What's the origin of "slow boat to China"?

Since I will likely be spending the month of June in China, I thought it would be helpful to know in advance where the phrase "A slow boat to China" came from.

— John B.

The phrase was popularized by the song "On a Slow Boat to China," written by Frank Loesser (1910-1969), copyrighted in May 1948. Loesser is perhaps the most versatile of all Broadway composers, having written the music for such famous shows as Where's Charley (1948), Guys and Dolls (1950), Most Happy Fella (1956), and How to Succeed in Business Without Really Trying (1961). He composed music for films such as College Swing (1938), Destry Rides Again (1939), Fred Astaire's Let's Dance, and Hans Christian Andersen (1952).

Loesser wrote such standards as "Two Sleepy People," "Heart and Soul," "I Don't Want to Walk Without You," "Spring Will Be a Little Late This Year," "(See What) The Boys in the Backroom (Will Have)," "They're Either Too Young or Too Old" and his 1948 Academy Award winner, "Baby, It's Cold Outside," in addition to "On a Slow Boat to China."

The lyrics for "Slow Boat to China" start:

I'd love to get you
On a slow boat to China,
All to myself alone.
Get you to keep you in my arms evermore,
Leave all your lovers
Weeping on the faraway shore.

Loesser wrote and circulated the song in 1945, but did not get a copyright until 1948.

Where did he get the phrase? His daughter, Susan Loesser, author of a biography of her father, A Most Remarkable Fella (1993), writes:

"I'd like to get you on a slow boat to China" was a well-known phrase among poker players, referring to a person who lost steadily and handsomely. My father turned it into a romantic song, placing the title in the mainstream of catch-phrases in 1947.

The idea, of course, was that traveling by boat to China was about as long and slow a trip as one could imagine. Loesser moved the phrase from the poker table to a more romantic setting. The song was very popular in its time (and has been revived and sung from time to time over the years by such notables as Kay Kyser, Bing Crosby, Jimmy Buffett, and Frank Sinatra, among others). The phrase then moved into general parlance to mean anything that takes a lonnnnnnng time.

— Dex and SamClem

Staff Reports are written by the Straight Dope Science Advisory Board, Cecil's online auxiliary. Though the SDSAB does its best, these columns are edited by Ed Zotti, not Cecil, so accuracywise you'd better keep your fingers crossed.